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Technical Bulletin Series North Central Regional Center Technical Bulletin Series An Overview of Aquaponic Systems: Hydroponic Components D. Allen Pattillo1

Introduction is the union of (growing without ) and aquaculture (farming or other aquatic organisms) for a fast, efficient method of producing both and fish . Fish waste from the aquaculture portion of the system, is broken down by bacteria into dissolved (e.g., and compounds) that plants utilize to grow in a hydroponic unit (Figure 1). This removal not only improves quality for the fish but also decreases overall water consumption by limiting the amount released as effluent. Aquaponics shares many of the advantages that hydroponics has over conventional production methods including: Figure 1. Components of an aquaponic system. 1. reduced land area requirements, 2. reduced water consumption, High-value herbs, vegetables, and leafy greens, as well as 3. accelerated plant growth rates, and fish, crayfish, worms, and a number of other products can 4. year-round production in controlled environments. be produced to meet a highly diversified market. Because aquaponic systems are often closed-loop systems (i.e., waste This growing technique reduces crop production time generated during production is recycled within the system), considerably. For example, butterhead varieties can nutrient effluence is virtually non-existent, allowing be produced in about 30 days, as opposed to the typical to take a large step toward environmental 60-day growing period needed under conventional methods. sustainability. Moreover, fish, plant, and waste solids can be In the North Central Region (NCR) of the United States, captured and converted into products for additional aquaponic operations are typically operated year-round in sale. These benefits make aquaponic systems a viable option a or other controlled environment, which allow for and producers who have limited space, giving producers to take advantage of higher seasonal produce more people access to locally produced, healthy foods. prices in the winter. This publication is part of an aquaponics series with Aquaponics has additional advantages: information relevant to the NCR and will cover the five 1. operational efficiency with shared equipment and most common categories of hydroponic crop production 2. multiple crops produced simultaneously. techniques, controlled environments, and mineralization.

1 Iowa State University Extension and Outreach Technical Bulletin #123 March 2017 Technical Bulletin Series

Hydroponic Growing Methods Used In Aquaponics There are many ways to grow plants hydroponically and many of these techniques have been adapted for use in aquaponic systems. The five most common categories of hydroponic growing methods used in aquaponic systems include flood and drain, , , drip , and vertical growing systems. Each of these methods are effective at growing plants, but certain systems may be favorable under different scenarios. Figure 2 describes the aquaponic system developed at Iowa State University.

Figure 3. A large flood and drain grow bed.

the plant to tolerate their sitting in water, duration of this cycle will vary. The Iowa State system has successfully grown leafy greens using a 15-minute flooding and 45-minute draining cycle during the 12 daylight hours, which is achieved with a 150 gallon/hour (550 liter/hour) pump on an electric timer.

Automatic siphons are used to quickly drain the hydroponic unit. This is generally achieved by using a loop siphon with either hard or soft plumbing, or a bell siphon (Figure 4). A siphon (Figure 5) occurs when water in a Figure 2. Schematic representation of the aquaponic system used vessel at a raised elevation has a tube or pipe submerged in at Iowa State University. it, and that tube, when completely filled with water and no air, creates a vacuum that allows the water to be transported Flood and Drain – Flood and drain (a.k.a. ; from one vessel to another by gravity flow. A bell siphon Figure 3) irrigates the plants by filling the hydroponic unit uses an inverted chamber encompassing a stand pipe that with nutrient-rich water followed by a period of draining, which draws air into the zone. The periodic emersion in water, followed by air exposure, introduces to the roots, producing an environment conducive to healthy roots. This method requires the use of a coarse substrate like , expanded clay, , and others to support the plant roots, while providing excellent . Flood and drain systems utilize the substrate for both root stability and the high surface area of the substrate for biological filtration.

Cycling between wet and dry can be controlled by several methods including a pump on a timer, an indexing irrigation valve, or the automatic siphon method. Generally hydroponic units are drained every 20-30 minutes to incorporate oxygen in the root zone. Depending on the Figure 4. A bell siphon chamber (left) and stand pipe inside a moisture holding capacity of the substrate and the ability of permeable pipe (right).

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creates an air lock causing a siphon to form as the air exits from the chamber, and the water continues to flow until air is reintroduced into the chamber through the arches at the bottom of the chamber. Flow rate and pipe diameter ratios are Figure 6. Deepwater culture using a floating raft. critical in creating Oxygen content in the water can be a major struggle Figure 5. Basic diagram of a siphon. this phenomenon, as greater flow in deepwater culture because of the high biological rates are needed to create suction required to evacuate air oxygen demand (BOD), defined as the need for oxygen from the chamber. If the gap between the standpipe and the for respiration by the plants, animals, and bacteria in this chamber is too great a siphon will not form, but if it is too biologically-rich system. Aeration should be supplied via narrow the siphon will break before the hydroponic unit diffusor airstones placed every 4 feet (1.2 meters) under the is drained. rafts to prevent stagnation and oxygen deprivation in the root zone. The outflow from the hydroponic unit should be guarded by a permeable pipe (Figure 4) that will hold back the When using this method, water depths may range from substrate while allowing water to flow freely through 4 inches (10 cm) to 3 feet (1 m) or more, but a typical it. Care should be taken to keep the plumbing flow depth is 12-24 inches (30-60 cm). Although there are unobstructed, as small diameter gravel will tend to fall into commercially available containers created specifically the outflow pipes. In the Iowa State system, an 8-inch (20- for deepwater culture of plants, many hobbyists choose cm) section of 4-inch (10-cm) diameter corrugated plastic to construct their own using a variety of materials and tile drain line with 1-inch (25-mm) slots is used to keep the dimensions. Since many do-it-yourselfers will go to the gravel substrate away from the drain. local home improvement store to purchase materials, system designs generally conform to the dimensions of the readily Deepwater Culture – This method, also known as available materials (e.g., 4-foot (1.2-m) increments) to floating raft culture, is the most commercially adopted reduce labor. Typical building materials include pressure technique because of its simplicity and reliability. treated lumber, galvanized steel tubing, or masonry blocks, Deepwater culture (Figure 6) uses a floating or suspended all of which are covered with a plastic, polyvinyl chloride platform with holes to support the plants and allows roots (PVC), heavy duty tarp, or rubber pond liner to hold to be submerged in the water. insulation is water. The materials are generally chosen for availability, typically used as the raft and plastic net pots support the price, durability, and structural stability depending on the plants, although some new food-grade materials have been volume, shape, and life expectancy of the container. Not all developed. The rafts provide many benefits including ease construction materials are considered food-grade, and care of use, mobility, simple cleaning, and lower risk of plant should be used in their selection, particularly if the produce mortality during power outages. Plants in a deep water is to be sold. culture unit may live up to 2 weeks without water flow or aeration as compared to hours or days in other systems.

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tubing that ranges in diameter based on the clarity of the water source and biofouling from bacteria and algae.

An advantage to this system is its light-weight design, which allows vertical installation of channels over one another or above a deepwater culture system. They should be spaced so light is able to penetrate all crops (Figure 8). The channels are mobile, making it easy to change row spacing or add or remove channels from the system, creating flexibility for harvest methods.

Small diameter irrigation line (spaghetti tubing) is prone to clogging in aquaponic systems and should be Figure 7. Nutrient film technique (NFT). avoided. Instead, replace the tubing with 5/8-inch (16-mm) diameter or greater hose (Figure 9). Inadequate flow rates, Nutrient Film Technique (NFT) – The nutrient film channelization of water flow, and clogging with massive technique (Figure 7) utilizes the contact of the root zone roots leading to nutrient deficiencies, wilting, variable crop with a thin film of water (approximately 1/4-1/2 inch production, and plant mortality. (5-10 mm) deep) that flows along a smooth surface where the roots of the plants can contact both air and water simultaneously. This is commonly done inside a channel or gutter style system made from white extruded PVC material. These channels vary in width (4-9 in or 10-23 mm) and depth (1.5-4 in or 4-10 cm), depending on the size of the plants being grown. Plants like basil and lettuce can be grown in smaller channels, whereas tomatoes, , and peppers are grown in larger channels to accommodate the larger root mass associated with the plants. The slope of these systems range between 1 and 4 percent (slope = rise/ run), and flow rates between 0.25-0.5 gallons (1-2 liters) per minute. Water is delivered into the channels via opaque Figure 9. Nutrient film technique modified for aquaponic systems with a hose.

Drip Irrigation – systems (Figure 10) use a substrate for growing plants that provides the root zone with a constant supply of water and air. Common methods include (Dutch or Bato) bucket culture and slab culture, and are typically used for large fruiting crops like tomatoes, cucumbers, and peppers. Bucket culture combines the concepts of flood and drain and NFT, creating a modular, mobile growing method for large vining crops. Bucket culture substrates generally include perlite, pea gravel, expanded clay, or rockwool.

Figure 8. Nutrient film technique (NFT) installed over deep water culture.

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Figure 11. Slab culture using drip irrigation.

Vertical Growing Systems – Vertical growing systems maximize the production output of a growing area by taking advantage of the 3-dimensional space, which may be important for in urban areas where growing space can be expensive. Vertical growing may involve multiple layers of deepwater culture, NFT (Figure 12), flood and drain systems, or growing towers that involve aeroponic growing methods, in which the plant roots are suspended in the air and sprayed with nutrient rich water (Figure 13).

Figure 10. Drip irrigation in bucket culture.

Slab culture (Figure 11) is similar to NFT culture, but the water is injected directly into the plant root zone. A commercially available, multi-stage growing method commonly used includes small (1-1.5 in or 2.5-4 cm diameter) starter plugs followed by an intermediate (4x4x4 inch or 10x10x10 cm) block and slab (6x6x24 in or 15x15x60 cm). The substrate is generally covered with plastic to prevent algae growth. Slabs, blocks, and plugs may be made of rockwool, coconut , or other materials. Coconut coir has the added sustainable benefit of being compostable. Figure 12. Vertical plant production using deep water culture and NFT.

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Table 1. Required nutrients for plant growth in aquaponic systems. Nutrient Type Nutrient (symbol) Nitrogen (N) Phosphorus (P) (K) * Macronutrient (S) (Ca) * (Mg) (Fe) * (Cl) (Mo) Micronutrient (B) (Cu) (Mn) (Zn)

* Denotes nutrients typically lacking from fish feeds.

A mineralization tank (Figure 14) is highly agitated with aeration, creating an opportunity for bacteria to consume waste products and liberate bioavailable nutrients. The process of bacterial digestion and breakdown of feed generally occurs under aerobic (oxygenated) conditions. Periodically aeration is stopped for a period of 20-60 minutes, allowing the solids to settle to the bottom. This process Figure 13. Vertical growing tower. clarifies the water, and the top water layer is then added to A growing tower is designed so that water is pumped the hydroponic unit. from the sump up to the top of the tower and onto a diffuser plate, creating “rain” inside the tower as it drips over the plant roots that are suspended in the air. Towers may be empty (hollow) or filled with a substrate that provides plant structure and aids in water dispersal. Biofouling in an aquaponic system is typical, and vertical systems are particularly susceptible to clogging and reduced flow rates that may starve the plants for water. A routine pressure washing of system components to remove any biofouling is highly recommended for success. Mineralization Fish feed typically has 10 of the 13 required nutrients (Table 1) plants need to thrive under aquaponic growing conditions. The three potential limiting nutrients are calcium (Ca), potassium (K), and iron (Fe). The remaining nutrients Figure 14. Aerated mineralization tank. are available for plant uptake after the feed is consumed by is a process that uses bacterial fish and later excreted as waste materials. These wastes are decomposition in an oxygen-free environment to break processed by bacteria present in a mature system. down the fish waste, producing gasses like methane (CH4)

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warehouse environment will require the use of artificial light, a major energy input. Farmers can work with their local power company to obtain reduced electrical pricing rates by using ‘off-peak’ power when the typical energy demand by other consumers is low (i.e., nights, weekends, and holidays). Operational efficiency can be gained by using the heat generated by certain types of grow lights and pumps used in the system to somewhat reduce heating requirements. Additionally, some producers choose to generate their own electricity with an internal combustion generator, creating electricity, heat, and – all Figure 15. Polycarbonate greenhouse growing environment. beneficial in plant production. that can be captured and burned as an electricity and heat Renewable energy sources are growing in popularity and source and generate CO2 for plants. This process also becoming more affordable for producers. Some government generates liquid fertilizer that can be added back to the programs provide incentives for using renewable energy hydroponic unit and solid fertilizer that can be used in the sources as well. Solar and wind energy are ways to reduce germination of seedling plants. a ’s carbon footprint and become more energetically independent from the power grid. Geothermal heating and Recent research suggests that a combination of aerobic cooling is one option for curtailing the summer and winter and anaerobic digestion techniques may benefit plant temperature variations experienced by greenhouse growers nutrient availability. Variations on these techniques may in the NCR. Installing these types of systems generally provide the optimal combined benefits of aerobic and requires a large investment, so farmers considering these anaerobic waste digestion. options should look into the capital cost of the infrastructure and compare it to the equipment’s useful lifespan as well the Controlled Growing Environment payback period required to recoup the upfront cost. The growing environment is critical for plant production. At present, the majority of available reliable aquaponics Conclusions research has been conducted in tropical climates where Aquaponic systems present a unique opportunity for growing conditions are ideal year-round. In the NCR, however, year-round production of plants and fish. Out-of-season hot summers and cold winters tend to limit the growing production of leafy greens, herbs, and vegetables can be season and production options available to producers. a major source of income for aquaponic producers, as Research and extension efforts are currently underway to they can take advantage of much higher seasonal prices. educate producers on optimized techniques in the NCR. The high quality and freshness of aquaponic produce is The ability to regulate temperature, light intensity, highly desired by chefs in metropolitan areas. If aquaponic humidity, and to shelter the production system from producers can fill the seasonal gaps with fresh produce, the elements helps optimize growth rates for crops as buyers are more likely to keep them as a vendor, allowing well as ensure biosecurity and food safety. A controlled producers to capture a larger market share. Additionally, environment may be a warehouse, classroom, basement, the local foods movement and consumer willingness to garage, greenhouse, or other structure that shields pay more for a superior product is a major advantage to the growing system from the external environment. aquaponic producers. (Figure 15) are commonly used for year-round Aquaponics can be done on a wide range of scales; crop production because of their heat retention and the from a bench-top aquarium for the hobbyist to a multi- of sunlight through the structure. Warehouses acre commercial facility capable of producing substantial have become popular for vertical growing systems because amounts of fish and plants per year. As in other agriculture of their availability in or near cities and their ability to operations, profitability in the aquaponics business insulate the crops from prevailing weather conditions. A model is related to scale and efficiency of production.

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Research conducted at Iowa State suggests that it may be run aquaponics facility, the ability to profit is greater as the possible to generate a profit when producing tilapia and plant growing area increases because of increased product basil in a greenhouse facility in Iowa. This system model output, efficient use of resources, stability of the system, and demonstrates that the value of the fish (tilapia) produced regularity of production. However, a larger facility does not has very little effect on profitability, but rather the price necessarily mean more profit. One should consider supply and amount of plants (basil) produced often determines and demand principles and wholesale versus retail pricing economic viability. to determine the actual returns to the . It is critical, therefore, for potential aquaponic farmers to do their due Aquaponics may be an attractive opportunity for diligence in business planning and market research as well individuals wanting to change their lifestyle to a slower pace as hands-on education prior to investing in an aquaponics with a modest income. In a well-designed and efficiently business to ensure success.

Suggested Readings Ako, H. 2014. How to Build and Operate a Simple Small-to-Large Scale Aquaponics System. Center for Tropical and Subtropical Aquaculture Center Publication 161. Available: http://www.ctsa.org/files/publications/CTSA_aquaponicsHowTo.pdf (Accessed March 3, 2017)

Ako, H. and A. Baker. 2009. Small-Scale Lettuce Production with Hydroponics or Aquaponics. SA-2. College of Tropical Agriculture and Human Resources. University of Hawaii at Manoa. Available: http://fisheries.tamu.edu/files/2013/10/Small-Scale-Lettuce-Production-with-Hydroponics-or-Aquaponics.pdf (Accessed March 3, 2017)

Burden, D. J. and D. A. Pattillo. 2013. Aquaponics. Agriculture Marketing Resource Center. Available: http://www.agmrc.org/commodities-products/aquaculture/aquaponics/ (Accessed March 3, 2017)

Conte, F. S. and L. C. Thompson. 2012. Aquaponics. California Aquaculture Extension. Available: http://fisheries.tamu.edu/files/2013/10/Aquaponics.pdf (Accessed March 3, 2017)

Diver, S. 2006. Aquaponics – Integration of Hydroponics with Aquaculture. ATTRA. Available: https://attra.ncat.org/attra-pub/download.php?id=56 (Accessed March 3, 2017)

Duncan, P. 2013. Introduction to Aquaponics Systems and Management. Available: http://fisheries.tamu.edu/files/2013/10/Introduction-to-Aquaponics-Systems-and-Management.pdf (Accessed March 3, 2017)

Engle, C. R. 2015. Economics of Aquaponics. Southern Regional Aquaculture Center Publication Number 5006. Available: https://srac-aquaponics.tamu.edu/serveFactSheet/8 (Accessed March 3, 2017)

Fox, B. K., R. Howerton, and C. S. Tamaru. 2010. Construction of Automatic Bell Siphons for Backyard Aquaponic Systems. Biotechnology BIO-10. University of Hawaii at Manoa. Available: http://www.ctahr.hawaii.edu/oc/freepubs/pdf/bio-10.pdf (Accessed March 3, 2017)

Kelly, A. M. 2015. Is Aquaponics for You? Realities and Potentials for Arkansas. University of Arkansas at Pine Bluff Extension. Available: http://cdm16039.contentdm.oclc.org/cdm/ref/collection/p266101coll7/id/28963 (Accessed March 3, 2017)

Kelly, A. M. 2013. Aquaponics. University of Arkansas Pine Bluff Extension. Available: http://fisheries.tamu.edu/files/2013/10/Aquaponics2.pdf (March 3, 2017)

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Mullins, B. Nerrie, and T. D. Sink. 2015. Principles of Small-Scale Aquaponics. Southern Regional Aquaculture Center Publication Number 5007. Available: https://srac-aquaponics.tamu.edu/serveFactSheet/9 (Accessed March 3, 2017)

Pattillo, D. A. 2015. Aquaponics Production Data: Loss or Profit? Iowa State University Extension and Outreach. Available: http://ohioaquaculture.org/pdf/aquaponics/Aquaponics%20Production%20data%20-%20loss%20or%20 profit%20Allen%20Patillo.pdf (Accessed March 3, 2017)

Pattillo, D. A. 2015. Aquaponics: Food Safety & Human Health. Iowa State University Extension and Outreach. Available: http://ohioaquaculture.org/pdf/aquaponics/Aquaponics%20Food%20Safety%20and%20Human%20 Health%20Allen%20Patillo.pdf (Accessed March 3, 2017)

Pattillo, D. A. 2014. Aquaponic System Design and Management. Iowa State University Extension and Outreach. Available: www.extension.iastate.edu/forestry/tri_state/tristate_2014/talks/PDFs/Aquaponic_System_Design_ and_Management.pdf (Accessed March 3, 2017)

Rakocy, J. E., M. P. Masser, and T. M. Losordo. 2006. Recirculating Aquaculture Tank Production Systems: Aquaponics – Integrating Fish and Plant Culture. Southern Regional Aquaculture Center Publication Number 454. Available: https://srac.tamu.edu/serveFactSheet/105 (Accessed March 3, 2017)

Rakocy, J. E., D. S. Bauley, R. C. Shultz, and J. J. Danaher. A Commercial-Scale Aquaponic System Developed at the University of the Virgin Islands. Available: http://ag.arizona.edu/azaqua/ista/ISTA9/FullPapers/Rakocy1.doc (Accessed March 3, 2017)

Resh, H. M. 1995. Hydroponic food production: a definitive guidebook for the advanced home and the commercial hydroponic grower, 6th Edition. Newconcept Press, Inc., Mahwah, New Jersey.

Rosen, C. J. P. M. Bierman, R. D. Eliason. Soil pH Modification. 2014. eXtension.org. Available: https://www.extension.org/pages/13064/soil-ph-modification#.VAh2yhCwWSo (Accessed March 3, 2017)

Sanders, D. 2001. Lettuce: Information Leaflet. North Carolina Extension. Available: http://content.ces.ncsu.edu/lettuce (Accessed March 3, 2017)

Sawyer, J. D. 2013. Aquaponics: Growing Fish and Plants Together. Colorado Aquaponics. Available: http://fisheries.tamu.edu/files/2013/10/Aquaponics-Growing-Fish-and-Plants-Together.pdf (Accessed March 3, 2017)

Somerville, C. Cohen, M. Pantanella, E. Stankus, A. and Lovatelli, A. 2014. Small-scale aquaponic food production: Integrated fish and plant farming. Food and Agriculture Organization of the United Nations: Fisheries and Aquaculture Technical Paper 589. Available: http://www.fao.org/3/a-i4021e.pdf (Accessed March 3, 2017)

Timmons, M. B. and J. M. Ebeling. 2013. Recirculating Aquaculture, 3rd Edition. Pp. 663-710. Northeastern Regional Aquaculture Center Publication No. 401-2013.

Tyson, R. 2013. Aquaponics – Vegetable and Fish Co-Production 2013. University of Florida Extension. Available: http://fisheries.tamu.edu/files/2013/10/Aquaponics-Vegetable-and-Fish-Co-Production-2013.pdf (Accessed March 3, 2017)

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Recommended Videos Danaher, J. 2015. Aquaponics – An Integrated Fish and Plant Production System. Southern Regional Aquaculture Center. Available: http://www.ncrac.org/video/aquaponics-integrated-fish-and-plant-production-system (Accessed March 3, 2017)

Pattillo, D. A. 2016. Aquaponics: How to Do It Yourself! North Central Regional Aquaculture Center Webinar Series. Accessed: http://www.ncrac.org/video/aquaponics-how-do-it-yourself (Accessed March 3, 2017)

Pattillo, D. A. 2013. Aquaponics System Design and Management. Iowa State University Extension and Outreach. Available: https://connect.extension.iastate.edu/p5fba9a68a0/?launcher=false&fcsContent=true&pbMode=normal (Accessed March 3, 2017)

Rode, R. 2013. Aquaponics. Available: https://www.youtube.com/watch?v=26xpMCXP9bw (Accessed March 3, 2017)

Ron, B. T. 2014. Aquaponics: Paradigm Shift with Airlift. eXtension.org. Available: https://www.youtube.com/watch?v=ZWGs4NIkrLs&feature=em-upload_owner (Accessed March 3, 2017)

Ron, B. T. 2014. Aquaponics: Paradigm Shift with Airlift Pumps Part 2. eXtension.org. Available: https://www.youtube.com/watch?v=1EDlMqrngqQ&feature=em-upload_owner (Accessed March 3, 2017) Resource Pages Agricultural Marketing Resource Center http://www.agmrc.org/

Aquaponics Association http://aquaponicsassociation.org/

Aquaponics Journal http://aquaponicsjournal.com

ATTRA National Center for https://attra.ncat.org/

Iowa State University Extension Online Store https://store.extension.iastate.edu

Iowa State University Food Safety Extension http://www.extension.iastate.edu/foodsafety/

Iowa State University Fisheries Extension http://www.nrem.iastate.edu/fisheries/

Leopold Center for Sustainable Agriculture https://www.leopold.iastate.edu/

North Central Regional Aquaculture Center www.ncrac.org

Southern Regional Aquaculture Center – Aquaponics Publication Series https://srac-aquaponics.tamu.edu/

Sustainable Agriculture Research and Education Program http://www.sare.org/

USDA – National Agricultural Library https://www.nal.usda.gov/afsic/aquaponics

University of Minnesota Aquaponics http://www.aquaponics.umn.edu/aquaponics-resources/

Texas A&M Aquaponics http://fisheries.tamu.edu/aquaponics/

Photos and figures provided by D. Allen Pattillo.

This material is based upon work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under award number 2012-38500-19550. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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